The present invention relates to a valve assembly for controlling fluid flow, more particularly such a valve assembly having dual valve seats to ensure the sealing of the fluid passageway.
Fluid feed valves located in a fluid conduit, or attached to fluid enclosures, such as tanks, to control the fluid flow from or between these elements are, of course, well known in the art. Typically, known valves have a valve body defining a valve seat against which a movable valve member may bear to close off the fluid flow passageway. Displacement of the movable valve member relative to the valve body moves the valve member away from the valve seat in order to open the fluid passageway and allow fluid to flow through the valve.
The valve member of the known valves is typically made of a hard material, such as steel, and the valve body is made of a softer material, such as a light alloy. The movable valve member may have a generally conical sealing surface which is designed to bear against the valve seat defined by the valve body, which may comprise a sharp edge. The sharp-edged construction of the valve seat enables the movable valve member to cut any foreign materials in the fluid which may be wedged between the valve seat and the sealing surface when the valve is closed. However, such foreign material may deleteriously effect the sealing of the valve seat by causing the movable member to be slightly skewed from its axis of travel. Quite obviously, this will prevent effective sealing of the valve assembly and render it largely ineffective. This drawback arises from the use of the sharp-edged valve seat to both cut the undesired foreign material, and to seal the fluid flow passageway.